1. Field of the Invention
This invention relates to 5-alkyl-6-[[amino]methyl]pyrido[2,3-d]pyrimidine compounds and pharmaceutically acceptable salts thereof. More specifically, it relates to compounds useful in resisting Pneumocystis carinii and Toxoplasmosis gondii infections in immunocompromised patients, such as, for example, patients with autoimmune deficiency syndrome (AIDS). These compounds may be useful, for example, as potential antitumor, antibiotic, antimalarial, antifungal or antiprotozoal agents or as synergistic agents with sulfonamides and may require the use of leucovorin rescue. Methods of preparing and using these compounds are also provided.
2. Description of the Prior Art
The pyrido[2,3-d]pyrimidine ring system has been studied due to its involvement in the inhibition of dihydrofolate reductase (DHFR) enzymes activity. The pyrido [2,3-d]pyrimidine derivatives inhibit the normal cell growth of a variety of cells. Methotrexate (MTX), trimetrexate (TMX) and piritrexim and other folic acid analogues function as inhibitors of cell growth by similar mechanisms involving the inhibition of dihydrofolate reductase. Inhibition of dihydrofolate reductase deprives the cell of 5,10-methylenetetrahydrofolate. 5, 10-methylenetetrahydrofolate is essential for cell growth. Dihydrofolate reductase reduces dihydrofolate to tetrahydrofolate. The inhibition of dihydrofolate reductase by the compounds and pharmaceutically acceptable salts of this invention results in the inhibition of DNA synthesis and leads to cell death.
Elslager, Edward F., et al., "Folate Antagonists. 20. Synthesis and Antitumor and Antimalarial Properties of Trimetrexate and Related 6-[(Phenylamino)methyl]-2,4-quinazolinediamines" J. Med. Chem., Vol. 26 pp. 1753-1760 (1983), discloses the preparation of quinazolinediamines. This article states that the quinazolinediamines exhibit potent antimalarial, antibacterial and antitumor activity.
Methods to synthesize diaminopyrido[2,3-d]pyrimidines having various substituents are known. See Hurlbert, B. S., et al., "Studies on Condensed Pyrimidine Systems. XXIII. Synthesis of 2,4-Diaminopyrido[2,3-d]pyrimidines from .beta.-Keto Esters", J. Med. Chem., Vol. 11, pp. 703-707 (1968), and Hurlbert, B. S., and Valenti, B. F., "Studies on Condensed Pyrimidine Systems. XXIV. The Condensation of 2,4,6-Triaminopyridimine with Malondialdehyde Derivatives", J. Med. Chem., Vol. 11, pp. 708-710 (1968).
Hurlbert, B. S., et al., "Studies on Condensed Pyrimidine Systems. XXV. 2,4-Diaminopyrido[2,3-d]pyrimidines. Biological Data", J. Med. Chem., Vol. 11, pp. 711-717 (1968), discloses the antimicrobial activities of several subgroups of pyridopyrimidines. This article states that 2,4-diaminopyrido[2,3-d]pyrimidines bearing alkyl and aralkyl substituents in the pyrimidine moiety are inhibitors of dihydrofolate reductases having antibacterial and antiprotozoal activity and that these compounds potentiate sulfonamides.
Grivsky, E. M., et al., "Synthesis and Antitumor Activity of 2,4-Diamino-6-(2,5-dimethoxybenzyl)-5-methylpyrido[2,3-d]pyridimine", J. Med. Chem., Vol. 23, pp. 327-329 (1980), discloses the synthesis of 2,4-diamino-6-(2,5-dimethoxybenzyl)-5-methylpyrido[2,3-d]pyridimine (BW301U,7). This article states that BW301U,7 is as effective as methotrexate as an inhibitor of dihydrofolate reductase purified from human leukemic cells and, in contrast to metoprine, has minimal activity as an inhibitor of histamine metabolism.
Werbel, Leslie M., et al., "Synthesis and Antimalarial Activity of a Series of 2,4-Diamino-6-[(N-alkylanilino)methyl]quinazolines [1,2]", J. Heterocyclic Chem., Vol. 24, pp. 345-349 (1987), discloses the synthesis of N6 substituted quinazoline dihydrofolate reductase inhibitors. This article states that these analogs demonstrate substantial activity against Plasmodium berghei infections in mice.
Piper, J. R., et al., "Syntheses and Antifolate Activity of 5-Methyl-5-deaza Analogues of Aminopterin, Methotrexate, Folic Acid, and N.sup.10 -Methylfolic Acid". J. Med. Chem., Vol. 29, pp. 1080-1087 (1986), discloses that 5-methyl-5-deaza analogues of aminopterin and methotrexate are much more growth inhibitory than methotrexate.
In spite of the prior art disclosures, there remains a very real and substantial need for an inhibitor of dihydrofolate reductases that is more active and more selective than known compounds having antitumor, antibiotic, antimalarial, antifungal or antiprotozoal activity or as synergistic agents with sulfonamides, and for methods of preparing and using such compounds.